Setting Up a bridge

vi /etc/network/interfaces

auto br0 iface br0 inet static

       pre-up brctl addbr br0
       pre-up echo 0 > /proc/sys/net/bridge/bridge-nf-call-arptables
       pre-up echo 0 > /proc/sys/net/bridge/bridge-nf-call-iptables
       pre-up echo 0 > /proc/sys/net/bridge/bridge-nf-call-ip6tables
       address 192.168.0.253
       netmask 255.255.255.0
       gateway 192.168.0.254
       post-down brctl delbr br0

auto eth0 iface eth0 inet manual

       up ip link set $IFACE up
       up brctl addif br0 $IFACE
       down brctl delif br0 $IFACE || true
       down ip link set $IFACE down

auto eth1 iface eth1 inet manual

       up ip link set $IFACE up
       up brctl addif br0 $IFACE

down brctl delif br0 $IFACE || true

       down ip link set $IFACE down

...

That way you create br0 with: ifup br0, and you can add/remove individual interfaces to the bridge with ifup eth0, ifdown eth0.